The Aobas were
completed in 1927 and incorporated a number of lessons learned from the
preceding Furutakas,
such as the desirability of twin main gun turrets. However, these
proved too heavy for the hull, which had to be reconstructed to take
the weight. The Furutakas
were later modernized to very closely resemble the Aobas, which were themselves
modernized in 1938-1940.